Automatic combustion control

ABSTRACT

The control of efficiency of combustion is effected by the use of a smoke detector and mechanical amplifier, and by solid state devices for the detection and amplification of electrical signals produced thereby, with the ultimate purpose of positioning a modulating-type electric motor which in turn adjusts a fuel oil valve and primary and secondary air valves or dampers by means of mechanical linkages. Either a single motor or three separate modulating-type electric motors can be used for the three combustion control functions, i.e., fuel valve positioning, primary air valve or damper positioning and secondary air valve or damper positioning.

Seider 1451 Jan. 21, 1975 AUTOMATIC COMBUSTION CONTROL 75 Inventor: Se mour Seider, H lett H b Primary Examiner-Edward Favors 1 ew at or Attorney, Agent, or Firm-Alan K. Roberts [73] Assignee: B.S.C. Industries Corp., Hewlett [57] ABSTRACT Harbor The control of efficiency of combustion is effected by [22] Fil d; D 19, 1973 the use of a smoke detector and mechanical amplifier,

I and by solid state devices for the detection and ampli- [211 Appl' 426323 fication of electrical signals produced thereby, with the ultimate purpose of positioning a modulating-type 52 us. 01. 431/76, 236/15 E clcctric motor which in turn adjusts a fuel valve 51 1111. C1. F23n 5/08 and P y and secondary air valves or dampers by 58 Field 6: Search 431/76, 79; 236/15 E means of mechanical linkagcs- Either a Single motor or three separate modulating-type electric motors can [56] References Cit d be used for the three combustion control functions, UNITED STATES PATENTS i.e., fuel valve positioning, primary air valve or 3,549,089 12/1970 116161611 236/15 E z ggg g and secm'dary valve or damper 3,701,622 10/1972 Ducasse p 3,723,047 3/1973 De Livois 431/76 33 Claims, 19 Drawing Figures 20 flI-l PATENTEDJANZ] I915 3,861,855

' sum 10F 6 FIG/ I PATENTEI] JANZ] I975 SHEET 2 OF 6 lq 9 LL AUTOMATIC COMBUSTION CONTROL FIELD OF INVENTION This invention relates to the automatic maintenance of a pre-set level of efficiency of combustion and is particularly useful for the control of the combustion of light to medium weight fuel oils, commonly referred to as No. 2 fuel oil and No. 4 fuel oil, in furnaces used for heating air, water, or for the production of steam. This invention is applicable to any fluid fuel, gas fuel or solid fuel such as powdered coal.

BACKGROUND Completely clear flue gas venting usually signifies excess air and lower efficiency of combustion. Heavier smoke of darker color and density usually signifies insufficient air and lower efficiency of combustion.

While there exist, at this time, many devices to measure smoke level in flue gases and to act, upon reaching a predetermined level, to sound an alarm, or to shut down the burner, or to provide combinations of these responses there does not exist, a simple, practical device that will, on attaining the pre-determined smoke level, automatically modulate the air-oil ratio to maintain that pre-determined level and thus maintain the combustion efficiency desired, without relying on manual resetting on the part of service personnel. The reason for this appears to reside in the insufficient sensitivity of existing devices which therefore do not permit discrimination between very low levels of smoke density as is necessary to maintain a close level of light smoke density in the flue gases.

Among the patents disclosing devices relating to the invention are the following:

From the above listed patents, it is believed pertinent to mention in detail only the Decker U.S. Pat. No. 1,987,433, the Brooke Jr. et a1. U.S. Pat. No. 2,285,564, the Logan U.S. Pat. No. 2,441,025 and the Dijt et al. U.S. Pat. No. 3,243,116.

With respect to the Decker Patent, this discloses improvements in the automatic control of combustion in furnaces. However, aside from the fact that this patent fails to disclose a smoke amplifier, the basic premises in this patent differ substantially from the apparatus to be disclosed hereinunder. Specifically, the Decker device is essentially a semi-manual device matching steam rate to a predetermined fuel rate. The draft in this device is adjusted to match the steamrate to the fuel rate. As a part of the control system, an automatic CO analyzer overrides the steam rate control. Also, an opacity device in the smoke stack furtheroverrides the steam rate control. There is no control of fuel rate but rather only a control of draft rate. Accordingly, as will be seen, this device is not comparable to the device provided in accordance with the invention.

The Brooke Patent also relates to combustion controls and is observed to be especially advantageous for furnaces using fluid fuel or the like including gas, oil or powdered coal. It is stated that the Brooke invention permits controlling combustion fluid according to the quality or character of the furnace gases in a reliable, accurate and satisfactory manner. As will be seen, this invention fails to disclose a smoke amplifier and thus cannot achieve the advantageous quality of control that is achieved in accordance with the invention. Moreover, this patent fails further to disclose any of the features which will become evident hereinafter.

As to the Logan U.S. Pat. No. 2,441,025, this patent also discloses improvement in automatic oil burner controls. Briefly, this patent discloses a system which will not work as efficiently as the system of the present invention, since it depends upon mechanical relays and unamplified smoke detection. The present invention, it willbe seen, is a definite improvement over what is disclosed by Logan.

With respect to the Dijt U.S. Pat. No. 3,243,l 16, the control methods are dissimilar from that which will be described below and there is no provision of smoke amplification.

The principal objection to the devices discussed above and the devices of the above listed patents is that they all fail to take into account that the ideal level of smoke is a relatively low level which cannot effectively be picked up by a smoke detecting means such as a photocell or photoelectric cell. This results in a relatively poor quality of control which is confirmed by the fact that none of the aforementioned devices have found substantial use in industry or in residential heatmg.

SUMMARY OF INVENTION In accordance with the invention, it is proposed to measure the smoke density in the smoke pipe or flue of a furnace by means of radiation from a uniformly radiating source such as an incandescent light bulb. The radiation falls on a photosensitive cell, preferably a cadmium-sulphide type cell, whose resistance to electrical unique feature of the invention to be explained in detail hereinafter.

By applying a fixed voltage across the resistance of a divider network including the photocell, a varying voltage is created. This voltage is amplified and fed to a solid state analog-to-digital converter. This solid state converter creates, for example, a four-bit word which represents the level of smoke detected by the photocell. These four-bit words trigger an appropriate triac switching circuit for controlling the resistance coupled to a modulating electric motor and, in turn, controlling its position, thereby controlling the air-oil ratio and, finally, the smoke level in the smoke pipe.

From the above, it will be noted that it is an object of the invention to provide an improved'combustion control apparatus. It is a further object of the invention to provide improvements which avoid the defects resulting from prior efforts to run control systems by the detection of a relatively low level of smoke density.

Yet another object of the invention is to provide an improved system which is relatively unsusceptible to deposits of soot or the like from the smoke being examined. Still another object of the invention is to provide a system which is relatively independent of the heat contained in the smoke being run through the detector system. Yet another object of the invention is to provide improvements which are readily adapted to currently existing equipment.

To achieve the above and other objects of the invention, there is more generally provided a combustion control apparatus comprising a fuel input means, control means for regulating said fuel input means, smoke density detecting means for detecting and measuring the density of smoke generated by combustion of said fuel and for adjusting said control means in accordance with said density, and smoke accumulating means for amplifying the density of said smoke to facilitate the detecting and measuring of the same by said detecting means.

According to a feature of the invention, the fuel input means may include further means for the introduction of an oxygen containing gas such as air into the input means, said control means and detecting means regulating the introduction of said gas by said further means.

According to another aspect of the invention, the combustion takes place in a combustion chamber and there is provided an admission means for the admission of an oxygen containing gas into said chamber, said control means and detecting means regulating the admission of said gas into the chamber by said admission means.

According to yet another feature of the invention, the aforesaid detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and overlapping said axis to accumulate smoke between the source and cell.

More particularly, the aforesaid shield may have a cross-section which is a segment of a circle. In addition, the cross-section may be a triangular or polyhedral segmentor any other such concave form, or partially concave sections protruding from each side of the flue, and being discontinuous, thus affording an opening to passage of a portion of the smoke through the concave form, the form being capable of accumulating smoke in such a manner as to constitute a smoke amplifier thereby facilitating the operation of the source of light and photoelectric cell combination.

In accordance with one aspect of the invention, the aforesaid control means may include a single motor for controlling all of the various controls. According to another aspect of the invention, separate motors may be employed for operating the various controls.

Advantageously, the aforesaid light source and photo-electric cell are supported by tubular supports on opposite sides of the flue through which passes the gas being examined. These supports may, in accordance with the invention, include sections of thermally insulating material to isolate the source and the cell thermally from the flue.

According to another advantageous aspect of the invention, the apparatus thereof includes blowers connected to the aforesaid tubular supports to pressurize the same and cool the source and cell and thereby to minimize contamination of the source and cell by solids from the smoke.

Yet another advantageous feature of the invention consists of an adjustable smoke deflector in the flue upstream of the smoke accumulating means to direct the smoke towards the accumulating means. The deflector can be mounted on hinges in the flue and means can be provided for adjusting the angle of the deflector in the flue.

According to still another aspect of the invention, the aforesaid control means has a regulating limit. In addition, there can be provided alarm means for indicating the reaching of said limit and delay means to prevent the actuating of said alarm means until the limit has been reached for a predetermined period of time.

According to another aspect of the invention, the fuel input means includes a fuel storage means, a pump connected to said storage means, a burner, a first valve coupling said pump to said burner, a plurality of return by-pass valves returning said fuel to said storage means to reduce the supply of fuel to said storage means and solenoid means to control said valves.

The aforesaid by-pass valves are advantageously arranged in cascade manner and the aforesaid solenoid means includes solenoids associated with the by-pass valves to control the same. In this arrangement, the first valve is a normally closed valve and the by-pass valves are normally open valves.

According to yet another aspect of the invention, the aforesaid control means includes a modulating motor coupled to the detecting means and mechanical linkage means coupling said motor to said fuel input means.

According to yet another aspect of the invention, the aforesaid control means includes a modulating motor, analog-to-digital conversion means being coupled to said detecting means, said detecting means generating an electrical signal which is converted into a digital signal by said conversion means and triac switch means controlled by said conversion means to operate said modulating motor.

Further, there may be provided an amplifier means coupled between the aforesaid detecting means and conversion means and offset control means coupled to said amplifier means. Still further there may be provided a voltage divider coupled to and controlled by said detecting means. Moreover, there may be provided a resistor network coupled between said motor and triac switch means.

The above and further objects and features of the invention will befound in the detailed description which follows hereinafter.

BRIEF DESCRIPTION OF DRAWING The invention will be explained hereinafter in connection with the associated drawing in which:

FIG. 1 is a diagrammatic illustration of an apparatus provided in accordance with one embodiment of the invention:

FIG. 2 is an enlarged view of a section of FIG. 1;

FIG. 3 is a sectional view taken along line IlI-III of FIG. 1;

FIG. 4 is a longitudinal section through a corresponding portion of the apparatus;

FIG. 5 is a chart illustrating the operation of the smoke accumulator means of the invention;

FIG. 6 is a block diagram of the electrical solid state circuitry by means of which the operation of the photo electric cell is converted into control signals and mechanical control action;

FIGS. 7(a) and 7(b) constitute, together, a schematic circuit diagram corresponding to the circuit shown in block diagram form in FIG. 6;

FIG. 8 illustrates a modification of the apparatus illustrated in FIG. 1;

FIG. 9 is a block diagram illustrating an alarm system for use with any of the aforegoing embodiments;

FIG. 10 illustrates an alarm system for use in connection with the embodiment of FIG. 8;

FIG. 11 is a diagrammatic illustration of a means for controlling the amount of fuel fed to the system of the invention;

FIG. 12 is a schematic view of the electrical portion of the apparatus illustrated in FIG. 11;

FIG. 13 is a perspective view of a part of the apparatus of FIG. 1; v

FIGS. l4(a)(d) arecross-sectional views through modified embodiments of the invention with respect to the smoke accumulator means; and

FIG. 15 is a top plan view of still a further form of smoke accumulator.

DETAILED DESCRIPTION As has been indicated above, FIGS. 1 and 2 diagrammatically show apparatus provided in accordance with one embodiment of the invention. This apparatus comprises a combustion chamber 20, a burner or injection nozzle 22, a flue 24 for the venting of gases from the combustion chamber 20, a smoke detector and amplifier section 26, a chimney 28 for the escape of flue gases and an electronic control section 30 which re sponds to the smoke detector and amplifier section 26 as indicated by the control line 32. A photoelectric cell 34 employed in accordance with the invention is indicated at 34 adjacent the section 20.

A modulating motor 36 is indicated atop the burner 22. It includes a displaceable control arm 38. By means of a link 40, the control arm 38 is connected to the oil valve 42 which controls the amount of oil admitted from the oil pipe 44 via extension 46 into the burner 22.

By means of a link 48, the arm 38 is connected to a primary air damper 50 which controls the admission of air or other such oxygen containing gas into the burner 22 via input pipe 52. The link 48 is furthermore connected via a link 54 to the secondary air damper 56 by measn of which control is effected on the amount of air which is admitted directly into the chamber 20.

The controller 30 is connected electrically to the motor 36 as indicated by connection 60. The controller 30 is itself controlled by the smoke amplifier and detector section 26 which will be more clearly understood by reference to FIGS. 3 and 4.

In FIGS. 3 and 4, it is seen that the section 26 consists of a casing which may be, for example, of rectangular cross-section and which is provided with flanges 72 which enable connection of the section into the flue of the furnace.

On opposite sides of the casing 70 are provided tubular sections 74 and 76. To these tubular sections 74 and 76 are respectively connected blowers 78 and 80. Extending from the tubular sections 74 and 76 are asbestos tubes 82 and 84, respectively, at the extremities of which are mounted casings 86 and 88.

The casing 88 is indicated diagrammatically as including alight source 90. The casing 86 is diagrammatically indicated as including a photocell or photoelectric cell 92. Defined between .the source 90 and the photoelectric cell is a sighting axis 94.

It will be observed that a concave shield 96 constituting a smoke amplifier is mounted adjacent the sighting axis 94 and in partially overlapping relationship with the same. It will be, moreover, observed that the shield 96 opens in the downstream direction relative to the direction of smoke travel indicated by arrow 98 or, in other words, the shield 94 opens in a direction opposite to the direction of travel of the smoke.

The provision of the shield 96 functions to amplify the smoke density. This is further aided by the provision of a deflector 100 which is mounted on a hinge 102 within the casing 70. The angular disposition of the deflector 100 is controlled by a threaded rod 104 which engages the hinged deflector by means of a rounded tip 106. The adjustment of the threaded rod 104 is controlled by a knob 108 and the rod 104 is locked in position by means of a lock not 110.

The deflector 100 serves to confine the passage for the flow of smoke into a throat section indicated at T. The smoke is therefore deflected in the illustrated example upwardly towards the shield 96 whereat an accumulation of smoke takes place and the density of smoke is amplified.

Surprisingly it has been found that the accumulation of smoke and thereby the amplification of density thereof takes place in a predictable manner which can be utilized to enable the photocell 92 to perform its function with greater efficiency and accuracy. The results of the amplification are more particularly indicated by the chart which appears in FIG. 5.

The chart appearing in FIG. 5 compares the relative smoke density in Ringelman Nos. as against resistance in ohms of the photoelectric cell. The abscissa of the chart shows relative smoke density and the ordinate shows resistance in ohms of the photoelectric cell. Curve shows the results with the smoke amplifier. Curve 122 shows the comparative results without the smoke amplifier. As appears in the box accompanying the chart of FIG. 5, the percentage difference at Ringelman No. l is 13 percent. At Ringelman No. 2, the difference is 27.2 percent. At Ringelman No. 3, the percentage difference is 39.6 percent. At Ringelman No. 4, the percentage difference is 85.5 percent. At Ringelman No. 5, the percentage difference is 233.3

percent. These differences have been found sufficient to convert a relatively ineffective structure into a highly efficient and accurate control and therefore the smoke shield of the invention constitutes an amplifier which is a very important feature of the invention.

In addition to the above, the provision of blowers 78 and 80 is a further feature of the invention inasmuch as these pressurize tubular extensions 74 and 76 and thereby impede the flow of soot and other such solids from the section 26 into the light source casing 88 and into the casing 86 for the photoelectric cell 92 thereby protecting these elements from the accumulation of dirt and thus in turn decreasing the need for maintenance and replacement. Furthermore, they particularly maintain the accuracy of response to the smoke levels in the flue gas by greatly reducing the spurious responses created by soot deposits on the light source and the photocell.

At the same time, the blowers 78 and 80 provide another significant advantage in that they reduce the temperatures of the operative elements by which smoke detection is effected whereby the longevity of these elements is much improved. As a result, they particularly maintain the accuracy of response to the smoke levels in the flue gas by greatly reducing the spurious re sponses by the photocell due to excessive changes in ambient temperature.

Still further, the provision of asbestos tubes 82 and 84 prevents the conduction of heat from tubular sections 74 and 76 to casings 86 and 88 whereby an additional protection against heat is afforded.

In FIG. 6 is indicated in block diagram form the electrical circuitry provided in accordance with the invention in association with the photoelectric cell 92 and the light source 90, the smoke amplifier and detector section 26 also being generally indicated along with the sighting axis 94.

In FIG. 6, it is particularly seen that there is provided a voltage divider indicated generally at 130, said voltage divider including a variable resistance 132 and a brush 134. The voltage divider also includes the photoelectric cell 92. A voltage is applied across the voltage divider by means of terminals 136 and 138. Variable resistor 132 is preferably set to equal the photocell resistance at a no-smoke or preferred smoke level. As a result, any voltage variation at junction 140 will be a direct indication of the resistance variation of the photocell 92 and therefore a direct indication of the obscuration caused by the smoke passing through the light beam generated by the light source 90.

The'voltage appearing at junction 140 is fed into an amplifier 142 to raise its level. An additional feature of the invention is provided at this point in the form of an offset control 144. The offset control, through the biasing of the solid state amplifier 142, provides for a manual adjustment to place the initial no-smoke" voltage reading into anyone of four quantization regions. In affect, this allows a very simple method of setting the zero point of the associated modulating motor which is the point about which the modulating motor will operate. This feature obviates the necessity of changing the aforedescribed linkages whenever a small adjustment is necessary in order to change the range of movement of the associated oil valves and the associated air dampers.

The voltage output for the amplifier 142 is fed to the analog-to-digital converter 146. The purpose of this converter is to change the analog input from the preceding state into a digital word outputof, for example, 4 bits. This output is fed into a digital amplifier and triac switching section 148 which first amplifies the digital word input to the necessary levels and then reads the input word in such a manner as to switch or gate one of a series of triac switches. This gating or switching action of the triac switches connects the common lead output of the resistor network 150 to a different point in the network. As the network is connected in a potentiometer configuration, its three wire output is suitable for direct connection to a three-wire-input modulating type motor such as is employed to constitute the motor 36 (see also FIGS. 1 and 2).

In this example, the total resistance across the potentiometer connected resistance network 150 is ohms to match the input requirement of a Honeywell M 900 series modulating type motor. It can as well be very simply changed to the 270 ohms required by the same motor when used with other primary controls or to any desired value of resistance to match any input characteristic desired for any model of suitable modulating motor.

It is to be noted that each triac gating switch in the amplifier and triac gate switch section 148 is singly operated as the input signal strength reaches the particular quantization setting of that particular triac, which input signal is fed to it by the analog-to-digital converter 146.

It has been found from trial and experience that six gates and therefore six steps of resistance variation in the output of the resistor network give a very satisfactory level of sensitivity of control for the modulating motor. Therefore, although discussion hereinunder may describe a different number of gating devices, it is to be understood that any number of gating devices may be employed but that six or more are preferable.

In the above-noted arrangement, the smoke detector and amplifier have been shown as being mounted horizontally. It can as well be mounted vertically. In the latter event, the position of the shield, with respect to the deflector is less significant. When the shield is mounted horizontally, it must be mounted so that the variable deflector is at a lower level than is the shield or collector baffle.

A schematic diagram of a circuit constituting the block diagram of FIG. 6 appears in FIGS. 7(a) and (b) wherein can be seen the photoelectric cell 92, the variable resistor 132, brush 134, junction 140 and voltage input terminals 136 and 138.

Junction 140 is connected via a resistor to the negative input of an operational amplifier 172. The positive input terminal of this operational amplifier is connected via a tap 174 on a resistor 176 which is connected across the photoelectric cell 92 and the variable resistor 132. The operational amplifier 172 has a variable feedback resistor 178 and the output of the operational amplifier 172 is connected via resistor 180 to line 182 which is connected to the positive input terminals of operational amplifier 184, 186 and 190 and to the negative input terminals of operational amplifiers 188, 192 and 194.

A line 196 is provided which is connected between resistors 198 and 200. Resistor 198 is connected to ground at a terminal 202. Line 196 is connected to the negative input terminal of operational amplifier 184 and to the positive input terminal of operational amplifier 188.

In addition to the above, there are further provided resistors 210 and 212 connected to a junction 214. Resistor 212 is connected to voltage source terminal 138 whereas resistor 210 is connected to ground at terminal 202. Junction 214 is connected to the negative input of operational amplifier 190 and to the positive input of operational amplifier 194.

The output of operational amplifier 184 is connected to NAND gate 220. The outputs of operational amplifier I86 and 188 are connected to NAND gate 222. The outputs of operational amplifier 190 and 192 are connected to both inputs of NAND gate 224 and the output of operational amplifier 194 is connted to both inputs of NAND gate 226.

Also included in the circuit illustrated in FIG. 7 are operational amplifiers 228, 230, 232 and 234. The positive input terminal of operational amplifier 228 is connected to NAND gate 220 whereas the negative input of operational amplifier 228 is connected via line 236 to ground as are the negative input terminals of operational amplifiers 230, 232 and 234.

The positive input terminal of operational amplifier 230 is connected to the output of NAND gate 222 whereas the positive input terminals of operational amplifier 232 and 234 are connected to the outputs of NAND gates 224 and 226 respectively. The output terminals of operational amplifier 228, 230, 232 and 234 are respectively connected to transistors 238, 240, 242 and 244. The collectors of these transistors are respectively connected to triac switches 246, 248, 250 and 252. The emitters of he transistors are connected to -6 volts at terminal 136 via resistors 247, 249, 251 and 252.

A resistor 254 is connected to triac 250 and resistors 256 and 258 are connected to triac 246 and to output terminal 260. Output terminal 262 is connected via resistor 264 to triac 252 which is connected to triac 250 by resistor 266. Output terminal 268 is connected to ground terminal 202.

In FIG. 7(b), it is seen that motor M includes two balancing relay coils Cl and C2 with terminals T1 and T2 connected respectively to terminal 268 and to variable resistor R. The shaft Sof the motor M also appears and is directly connected to brush B. Shaft S operates to control brush B to maintain balanced current in coils Cl and C2.

In the above, the operational amplifiers may be Fairchild operational Amplifiers p. A747 or equivalents thereof. The aforesaid NAND gates may be I.C. RCA 40ll NAND gates or equivalents thereof. The above noted transistors may be Motorola transistors 2N2905A or equivalents thereof. The triacs may be RCA triacs 40528 or equivalents. The circuitry shown in schematic form operates generally as indicated hereinabove with respect to the block diagram appearing in FIG. 6.

Whereas a single modulating type motor has been indicated as operative with respect to all controls in connection with the above described embodiment of the invention, FIG. 8 indicates the use of a plurality of modulating type motors for effecting each of the controls. More particularly, the burner 22 discharging into combustion chamber 20 can be seen in FIG. 8 along with oil valve 42 and dampers 50 and 56. Contrary to the preceding embodiment of the invention, there are here seen modulating motors 280, 282 and 284 all operating independently in the manner indicated above with respect to motor 36. In this embodiment of the invention, however, motor 280 controls the oil valve 42 separately from the control of dampers 50 and 56 and motors 282 and 284 respectively and separately control dampers 56 and 50.

The three motor modification provides a much simpler installation as only electrical connections need be made. This avoids the installation of the rod linkages mentioned hereinabove as well as their individual adjustments and the maintenance of such adjustments. In addition, the use of separate motors provides a much more flexible control of three functions because, by electrical. switching only, the three motors can be driven in unison as to direction or any one or more of the three motors can be reversed with respect to the others. This is easily accomplished by means of switching methods well known in the art and derivable from what has been described hereinabove.

A further feature of the invention is shown in FIGS. 9 and 10. In FIG. 9, the single modulating motor embodiment is shown with a single-pole double-throw switch 290 being mounted at the end of the shaft of the modulating motor 36 with which it is associated. If the situation should arise that the motor 36 is driven beyond its normal operating range to an extreme position, this would be indicated by the end switch 290. This would operate in turn to energize the time delay relay 292 which in turn would operate the associated and connected alarm 294. Therefore, after a predetermined and preset delay of, for example, 30 seconds, a system would operate to shut off the associated burner and would also operate a suitable alarm or set of alarms diagrammatically indicated at 294.

The purpose of this alarm and shut-down capability is that if the modulating motor is at an extreme period for more than a predetermined period of time, then the situation being examined by the automatic control system is of such severity as to be beyond the ability of the system to correct it. This extreme condition might be caused by grossly excess smoke, a mechanical or electrical failure or fault or by other such circumstances as might cause the modulating motor to assume a position which is antithetic to good operation and to maintain it beyond a prescribed limit. In this embodiment, the invention adds the capability of a smoke shut-down device.

FIG. 10 illustrates the same capability with respect to separate motors 280, 282 and 284 which, in such embodiments, are provided with end switches 296, 298 and 300 respectively. Herein, all of the end switches are connected to delay device 302 which, in turn, is connected to an alarm system 304 which represents both an alarm and a capability of shutting down the associated burner.

FIG. ll shows an accessory device to further expand the usefulness of the invention. This figure shows a four-step modulating control system which when used in conjunction with the efficiency and control system described above will permit limiting the firing rate from a predetermined low point to full capacity in four steps.

Practical experience has shown that a minimum firing rate of about 50 percent is the lowest that can be expected from an automatically controlled burner without service outages created by the fuel supply reduction although, as will be seen, any desired minimum fuel rate can easily be set into the control devices as can the size of the increments of the other three fuel rate steps.

In FIG. 11 is shown a fuel storage tank 320 connected to an outlet line 322 and a return line 324. An oil transfer pump 326 is provided, the output line of which is indicated at 328. Line 328 feeds into a normally closed solenoid-operated oil valve 330.

Referring, for example, to the embodiment illustrated in FIGS. 1 and 2, the accessory being described is attached to the oil valve 42 which feeds the burner 22 and which is controlled by the motor 36 for controlling combustion in the chamber 20.

In order to further control the oil flow to meet varying demand, three additional normally open solenoidoperated oil valves 332, 334 and 336 are provided and are connected to the line 328. These solenoid-operated oil valves respectively have metering orifices diagrammatically indicated at 338, 340 and 342 which in turn open into line 344 connected to return line 324 as is a by-pass line 346.

FIG. 12 shows the electrical connection for the above-described device. When the main temperature control device which may be, for example, a thermostat calls for heat, it closes a switch indicated at 360. Voltage is thereby applied to a primary oil burner combustion control such as a Honeywell No. 4147 or the like. When this control in the course of its cycle calls for the opening of the oil valve, a switch shown at 362 closes thereby applying voltage to the first stage of a four stage modulating controller 364. This controller may be either pressure actuated, a pressuretrol, an air temperature actuator mechanism, a thermostat, a water temperature actuator mechanism, an aquastat or any similar control device.

Assuming that there is a cold start and all for internal switchs 366, 368, 370 and 380 of controller 364 are calling for heat and hence are closed, voltage will be applied to the switch 366 and to relay coil 382 which will close, transferring voltage through contacts 384 to solenoid-controlled oil valve 330 causing it to open and allowing oil to enter the oil burner 22. As solenoid oil valves 332, 334 and 336 are normally open, much of the oil being pumped by pump 326 is by-passed back to the oil storage tank 320 via oil return line 324.

By selection of the size of the solenoid-operated oil valves and metering orifices, the amount of oil fed back to the burner at this stage of operation is limited to provide a suitable low-fire operation of the oil burner.

It should be noted at this point that, just prior to ignition of the fuel in the furnace 20, the smoke detector and amplifier section described hereinabove and the electronic controller see a clear smoke pipe and hence the primary air damper such as that indicated at 50 in FIG. 1 and the secondary damper 56 also seen in FIG. 1 will be in the minimum air position. This is the desired position for a low-fire start. The variable oil valves 42 (see FIGS. 1 and 11) will be in open position and will not at this point control the oil flow. Instead the solenoid-operated oil valve 330 will effect this control.

Voltage is also applied to the controller 364 and, particularly, the switch 368 through relay contacts 386. As it has been assumed that switch 370 is closed calling for heat, then voltage is applied to the primed delay relay 388 which will close after a predetermined time delay of, for example, 30 seconds. The purpose of this delay is to allow the fire to stabilize after having first been started by the opening of solenoid-operated oil valve 330 in the low-fire mode and also to allow the smoke efficiency regulating mechanism described above time to adjust the variable oil valve 42 and the associated dampers if necessary to adjust the fuel-air ratio for good combustion.

After the predetermined time delay, relay 388 will close applying voltage to its contacts closing the associated solenoid-operated oil valve 332 reducing the amount of oil being by-passed back to the oil storage tank 320. Voltage is sequentially applied to the next two relays 390 and 392 which operate in the manner described above so that eventually all of the valves 332, 334 and 336 will be closed whereby a maximum amount of oil will be fed to the burner 22 giving the high-fire operation desired.

As the controller 364 approaches its setting, its switches will start to open in reverse order. Switch 380 will open followed by the opening of switch 370 followed by the opening of switch 368. As each switch opens, its corresponding relay will open and the corresponding valve will open, reducing pressure at the oil burner thereby reducing fire size. Finally, the valve 330 will close shutting off oil flow to the burner in entirety.

As will be seen from the above description, the sections are connected in cascading arrangement. During the course of the cascading of the oil valve control both in upward and downward direction, the flame is monitored and controlled by the smoke detector and amplifier section and the electronic controller described above. A maximum efficiency is maintained along with a predetermined smoke level as has been described.

It can be seen that the cascading is managed by the controller 364 and that this may be held steady at any stage or may move in either direction from any stage to satisfy the input signals to the controller. It will also be seen that each stage requires a time delay and that no stage is skipped in the process of cascading upwards. Hence, it is not possible to get a high-tire start which is an important safety feature and frequently a legal requirement under the various safety codes.

It should be noted that the number of stages in the cascade arrangement is not critical. Four stages are used for the purposes of illustration. However, a very large burner might use more than four stages whereas a smaller burner might find two stages satisfactory.

It should be also noted that the controls shown with respect to FIGS. 11 and 12 incorporate electromechanical relays. These electromechanical relays can readily be replaced by solid state electronic devices.

FIG. 13 shows some mechanical details relating to FIG. 1 which also illustrates chamber 20, burner 22, motor 26, arm 38, valve 42, link 54 and damper 56. Also appearing in FIG. 13 are links 400 and 402 for rotating pivots, 404 and 406 which respectively control oil valve 42 and damper 50 (see FIG. 1). Other forms of mechanical arrangements are also possible.

From what has been stated hereinabove, it will now be appreciated that there is provided in accordance with the invention a combustion control apparatus comprising a fuel input means, control means for regulating the fuel input means, smoke density detecting means for detecting and measuring the density of the smoke generated by combustion of the fuel and for adjusting the control means in accordance with said density, and smoke accumulating means for amplifying the density of the smoke to facilitate the detecting and measuring of the same by said detecting means. Further refinements, arrangements and accessories have also been indicated.

While a smoke accumulator has been described above which has generally the form of a segment of a circle, other forms of such shields are possible, as has been indicated hereinabove. Thus, for example, a triangular shield is indicated at 450 in FIG. 14(a), a section of a polygon is indicated at 452 in FIG. 14(b), a further form of a section of a polygon is indicated at 454 in FIG. 14(c) and a further possible section involving the use of multiple sides is indicated at 456 in FIG. 14(d). v

In the above description, the shields employed as smoke accumulators extended continuously from one side of the flue to the other. This is not necessarily required. Each such shield may be broken up into two or more parts extending transversely of the flue, such as indicated at 460 and 462 in FIG. 15. Moreover, the shields may be provided with vents or slots, such as are generally indicated at 464 and 466 in FIG. 15.

The aforegoing variations are illustrative only and are not intended to be limiting of the invention inasmuch as many oter modifications are possible within the scope of the invention. Thus, for example, the slots or vents appearing in FIG. 15 may as well be applied to the variations illustrated in FIGS. l4(a)-(d) or to the type of shield indicated earlier in this description.

There will now be obvious to those skilled in the art many modifications andvariations of the constructions and circuits set forth hereinabove. These modifications and variations will not depart from the scope of the invention if defined by the following claims.

What is claimed is:

l. Combustion control apparatus comprising a fuel input means, control means for regulating said fuel input means, smoke density detecting means for detecting and measuring the density of smoke generated by combustion of said fuel and for adjusting said control means in accordance with said density, and smoke accumulating means for amplifying the density of said smoke to facilitate the detecting and measuring of the same by said detecting means.

2. Apparatus as claimed in claim 1 wherein said fuel input means includes further means for the introduction of an oxygen containing gas into said input means, said control means and detecting means regulating the introduction of said gas by said further means.

3. Apparatus as claimed in claim 1 comprising a combustion chamber, and admission means for the admission of an oxygen containing gas into said chamber, said control means and detecting means regulating the admission of said gas into the chamber by said admission means.

4. Apparatus as claimed in claim 3 wherein said fuel input means includes further means for the introduction of an oxygen containing gas into said input means, said control means and detecting means regulating the introduction of said gas by said further means.

5. Apparatus as claimed in claim 1 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.

6. Apparatus as claimed in claim 2 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.

7. Apparatus as claimed in claim 3 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.

8. Apparatus as claimed in claim 4 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to to accumulate smoke between the source and cell.

9. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is a segment of a circle.

10. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is triangular.

11. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is a segment of a polygon.

12. Apparatus as claimed in claim 2 wherein said control means includes a single motor for controlling both said fuel input means and said further means.

13. Apparatus as claimed in claim 3 wherein said control means includes a single motor for controlling both said fuel input means and said admission means.

14. Apparatus as claimed in claim 4 wherein said control means includes a single motor for controlling said fuel input means, said further means and said admission means.

15. Apparatus as claimed in claim 2 wherein said control means includes separate motors for controlling said fuel input means and said further means.

16. Apparatus as claimed in claim 3 wherein said control means includes separate motors for controlling said fuel input means and said admission means.

17. Apparatus as claimed in claim 4 wherein said control means includes separate motors for controlling said fuel input means, said further means and said admission means.

18. Apparatus as claimed in claim 5 comprising tubular supports respectively supporting said source and cell in opposite sides of said flue.

19. Apparatus as claimed in claim 18 wherein said supports include sections of thermally insulating material to isolate the source and cell thermally from said flue.

20. Apparatusas claimed in claim 18 comprising blowers connected to said tubular supports to pressurize the same and cool the said source and cell and to minimize contamination of the source and cell by solids from the smoke.

21. Apparatus as claimed in claim 1 comprising an adjustable smoke deflector in the flue upstream of said smoke accumulating means to direct said smoke towrads the accumulating means.

22. Apparatus as claimed in claim 21 comprising means hingeably supporting said deflector in the flue and means for adjusting the angle of the deflector in said flue.

23. Apparatus as claimed in claim 1, wherein said control means has a regulating limit, comprising alarm means for indicating the reaching of said limit and delay means to prevent the actuation of said alarm means until the limit has been reached for a predetermined period of time.

24. Apparatus as claimed in claim 1 wherein said fuel input means includes a fuel storage means, a pump connected to said storage means, a burner, a first valve coupling said pump to said burner, a plurality of return by-pass valves returning said fuel to said storage means to reduce the supply of fuel to said storage means, and solenoid means to control said valves.

25. Apparatus as claimed in claim 24 wherein said by-pass valves and in cascade arrangement and said solenoid means includes solenoids associated with the bypass valves to control the latter.

26. Apparatus as claimed in claim 25 wherein said first valve is a normally closed valve and the by-pass valves are normally open valves.

27. Apparatus as claimed in claim 1 wherein said control means includes a modulating motor coupled to said detecting means and mechanical linkage means coupling said motor to said fuel input means.

28. Apparatus as claimed in claim 1 wherein said control means includes a modulating motor, analog to digital conversion means coupled to said detecting means, said detecting means generating an electrical signal which is converted into a digital signal by said conversion means, and triac switch means controlled by said conversion means to operate said modulating motor.

29. Apparatus as claimed in claim 28 comprising an amplifier means coupled between said detecting means and conversion means, and offset control means coupled to said amplifier means.

30. Apparatus as claimed in claim 29 comprising a voltage divider coupled to and controlled by said detecting means.

31. Apparatus as claimed in claim 30 comprising a resistor network coupled between said motor and triac switch means.

32. Apparatus as claimed in claim 5 wherein said shield includes a plurality of spaced parts arranged transversely of said flue.

33. Apparatus as claimed in claim 5 wherein said shield is provided with at least one vent. 

1. Combustion control apparatus comprising a fuel input means, control means for regulating said fuel input means, smoke density detecting means for detecting and measuring the density of smoke generated by combustion of said fuel aNd for adjusting said control means in accordance with said density, and smoke accumulating means for amplifying the density of said smoke to facilitate the detecting and measuring of the same by said detecting means.
 2. Apparatus as claimed in claim 1 wherein said fuel input means includes further means for the introduction of an oxygen containing gas into said input means, said control means and detecting means regulating the introduction of said gas by said further means.
 3. Apparatus as claimed in claim 1 comprising a combustion chamber, and admission means for the admission of an oxygen containing gas into said chamber, said control means and detecting means regulating the admission of said gas into the chamber by said admission means.
 4. Apparatus as claimed in claim 3 wherein said fuel input means includes further means for the introduction of an oxygen containing gas into said input means, said control means and detecting means regulating the introduction of said gas by said further means.
 5. Apparatus as claimed in claim 1 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.
 6. Apparatus as claimed in claim 2 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.
 7. Apparatus as claimed in claim 3 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to accumulate smoke between the source and cell.
 8. Apparatus as claimed in claim 4 comprising a flue for venting said smoke and wherein said detecting means includes a source of light and a photoelectric cell arranged transversely of said flue and defining a sighting axis, said amplifying means including a concave shield facing against the direction of travel of the smoke in said flue and at least overlapping said axis to to accumulate smoke between the source and cell.
 9. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is a segment of a circle.
 10. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is triangular.
 11. Apparatus as claimed in claim 5 wherein said shield has a cross-section which is a segment of a polygon.
 12. Apparatus as claimed in claim 2 wherein said control means includes a single motor for controlling both said fuel input means and said further means.
 13. Apparatus as claimed in claim 3 wherein said control means includes a single motor for controlling both said fuel input means and said admission means.
 14. Apparatus as claimed in claim 4 wherein said control means includes a single motor for controlling said fuel input means, said further means and said admission means.
 15. Apparatus as claimed in claim 2 wherein said control means includes separate motors for controlling said fuel input means and said further means.
 16. Apparatus as claimed in claim 3 wherein said control means includes separate motors for controlling said fuel input means and said admission means.
 17. Apparatus as claimed in claim 4 wherein said control means includes separate motors for controlling said fuel input means, said further means and said admission means.
 18. Apparatus as cLaimed in claim 5 comprising tubular supports respectively supporting said source and cell in opposite sides of said flue.
 19. Apparatus as claimed in claim 18 wherein said supports include sections of thermally insulating material to isolate the source and cell thermally from said flue.
 20. Apparatus as claimed in claim 18 comprising blowers connected to said tubular supports to pressurize the same and cool the said source and cell and to minimize contamination of the source and cell by solids from the smoke.
 21. Apparatus as claimed in claim 1 comprising an adjustable smoke deflector in the flue upstream of said smoke accumulating means to direct said smoke towrads the accumulating means.
 22. Apparatus as claimed in claim 21 comprising means hingeably supporting said deflector in the flue and means for adjusting the angle of the deflector in said flue.
 23. Apparatus as claimed in claim 1, wherein said control means has a regulating limit, comprising alarm means for indicating the reaching of said limit and delay means to prevent the actuation of said alarm means until the limit has been reached for a predetermined period of time.
 24. Apparatus as claimed in claim 1 wherein said fuel input means includes a fuel storage means, a pump connected to said storage means, a burner, a first valve coupling said pump to said burner, a plurality of return by-pass valves returning said fuel to said storage means to reduce the supply of fuel to said storage means, and solenoid means to control said valves.
 25. Apparatus as claimed in claim 24 wherein said by-pass valves and in cascade arrangement and said solenoid means includes solenoids associated with the by-pass valves to control the latter.
 26. Apparatus as claimed in claim 25 wherein said first valve is a normally closed valve and the by-pass valves are normally open valves.
 27. Apparatus as claimed in claim 1 wherein said control means includes a modulating motor coupled to said detecting means and mechanical linkage means coupling said motor to said fuel input means.
 28. Apparatus as claimed in claim 1 wherein said control means includes a modulating motor, analog to digital conversion means coupled to said detecting means, said detecting means generating an electrical signal which is converted into a digital signal by said conversion means, and triac switch means controlled by said conversion means to operate said modulating motor.
 29. Apparatus as claimed in claim 28 comprising an amplifier means coupled between said detecting means and conversion means, and offset control means coupled to said amplifier means.
 30. Apparatus as claimed in claim 29 comprising a voltage divider coupled to and controlled by said detecting means.
 31. Apparatus as claimed in claim 30 comprising a resistor network coupled between said motor and triac switch means.
 32. Apparatus as claimed in claim 5 wherein said shield includes a plurality of spaced parts arranged transversely of said flue.
 33. Apparatus as claimed in claim 5 wherein said shield is provided with at least one vent. 